Myocardial infarction is a disabling disease, with infarct size being a major determinant of mortality. To limit infarct size and improve functional recovery, the ischemic myocardium has to be reperfused. However, reperfusion itself causes irreversible damage to the previously ischemic myocardium. A significant part of cardiac injury is caused by apoptosis that starts immediately at the beginning of reperfusion. Therefore, reperfusion injury is considered an important new pharmacologic target for the treatment of patients with ongoing acute myocardial infarction. We propose to develop a targeted liposomal formulation of two drugs proven to protect myocardium through independent mechanisms. Drug-carrying liposomes will be decorated with human annexin V for targeting to phosphatidylserine exposed on the surface of cardiomyocytes at the early stages of apoptosis. Intravenous administration of such liposomes immediately before the beginning of reperfusion could serve as an adjunct therapy for angioplasty and/or thrombolytic administration, which are the standard of care for patients with myocardial infarction. The advantages of the proposed strategy are: 1) delivery of pharmacologically significant amounts of drugs in cardiomyocytes from the first moments of reperfusion, when apoptosis is still reversible, 2) avoiding adverse effects of high-dose regimens that are necessary for free drugs, and 3) intracellular delivery of two drugs working via independent mechanisms increases the probability of successful treatment. Targeted drug-loaded liposomes will be evaluated in primary cultures of cardiomyocytes. We will establish mechanism(s) of internalization in early apoptotic cells and evaluate the therapeutic potential of annexin-targeted drug-loaded liposomes. Biodistribution, targeted drug delivery and the protective effects of the liposomes in vivo will be studied in a mouse model of myocardial ischemia/reperfusion. If successful, the proposed strategy will establish the feasibility of using annexin- targeted therapeutic liposomes as an adjunct therapy for myocardial infarction. It will also advance new technologies in developing therapeutic liposomes for targeted delivery to early-stage apoptotic cells. PUBLIC HEALTH RELEVANCE: We propose to test feasibility of developing a targeted liposomal formulation for two drugs proven to protect ischemic myocardium from lethal reperfusion injury through independent mechanisms. Drug-carrying liposomes will be decorated with human annexin V for targeting to phosphatidylserine exposed on the surface of cardiomyocites at the early stages of apoptosis. Intravenous administration of such liposomes immediately before the beginning of reperfusion could serve as an adjunct therapy for angioplasty and/or thrombolytic administration, which are the standard of care for patients with acute myocardial infarction.